Auto water pump is a device for conveying engine coolant, which contains mechanical pumps and electric pumps according to the driving mode, and electric pumps can be divided into brush electric water pumps and brushless electric water pumps. Mechanical pumps rely on the engine, and the fixed rate between pump speed and engine speed cannot meet the cooling requirements at low speed and high load, and when the engine stops, it is unable to meet the cooling requirements of main drive motor and other components of new energy vehicles as well as water supply requirements of motor homes. The brush electric water pump has poor anti-electromagnetic interference capability, and the brush tends to produce sparks that disturb other electronic devices. At the same time, influenced by the reversing carbon brush wear, the brush electric pump has a short service life, not suitable for new energy vehicles. Therefore, the DC brushless pump will be more and more used in high-end vehicles, new energy vehicles and motor homes.
The motor pump has following problems:
(1) The magnet of brushless DC magnetic drive pump and impeller are molded into a integrally composed rotor through injection, there is a sleeve in the center of the rotor fixed in the housing by high performance ceramic axis, and the stator portion of the motor and the circuit board is potted in the pump body by epoxy glue, thus the existing water pump has followings defects: difficulty of manufacturing technology, high production costs, difficult repair and media leaks, and the waterproof performance is not good, which affects the use of the motor. There are some motor pumps with separated rotor and impeller to the existing motor pumps, such as Publication No. CN 204591691U with the name of DC Brushless Auto Electric Water Pump. With distance sleeve, there is a cavity to accommodate the rotor. At the center of the inner bottom surface of the cavity, there is a lug boss to fix the pump shaft, one end of the shaft insert into the lug boss, rotation and axial movement are not allowed, and the other end of the shaft is inserted in the sleeve of the shaft head holder inside the pump head to separate the rotor and impeller in different spaces, which effectively prevents the medium leakage problems in the water pump, but with the problems of complex structure and inconvenient dismantling. Furthermore, the outlet of the DC brushless auto electric water pump faces the impeller, making the water flow be thrown out rapidly by a centrifugal force through the acceleration of the impeller, the noise of the water pump is large, the operation is unsteady and the service time of electric water pump is short.
(2) In addition, in the operation of water pump motor, the motor controller is easier to go wrong, the temperature increasing of motor is fast in the operation process of motor, and it keeps high temperature during the operation. It is likely to cause the controller burned and may reduce the life of the controller. Generally, the cooling equipment of the existing machine controller has heat sink or silicone pad and reduces the temperature of the controller through hot and cold air exchange. But the heat sink or silicone pad adopts the way of air heat exchange for heat dissipation, on one hand, the hot air generated by heat exchange cannot be exhausted out off the pump timely and as the long time operation of the motor, the cooling effect is decreased gradually, and on the other hand the heat dissipation effect of heat sink and the silicone pad itself is general which cannot effectively reduce the temperature of the controller.
(3) The impeller and rotor of the motor pump mounted together by a rotating shaft, generally the rotation shaft is graphite shaft. Rotation and axial movement exist during the operation. Axial movement can cause damage to the graphite shaft and the unsteady operation of motor. The existing installation methods generally suit the integrally molded impeller and rotor on the rotation shaft, which fix one end of the rotating shaft to the lug boss of the isolation sleeve, and fix the other end on the pump housing through shaft. The rotor moves at high speed, and the above installation cannot solve the problem of axial movement.